I can find no reference in published Pathfinder material to how many doses a completed Craft (alchemy) skill would yield as a result. It seems to me that only 1 dose would be of very limited use considering the time it consumes according to the rules.
e.g. Black adder venom (120gp, DC 11, 1d2 Con damage for 6 rounds) is one of the lower level poisons suggested in the CRB. After each week of work (and success on skill check), the progress is measured by multiplying the result of the check with the DC and comparing this resulting number to the price in sp=1200. So, a player would need a combined total of 110 (1200/11) on successful skill checks. That will most probably take several weeks to accomplish for a lower level PC.
So, how many doses does 'crafting a poison' yield according to the Pathfinder rules? Please provide reference to rules if you can. Or if there are no specific rules about this, what would be a reasonable assumption.